8.2.22. xilinx-zynq¶
This BSP supports the Xilinx Zynq range of devices. This family of devices contain the same ARM hard IP and the different parts have different sizes of programable logic.
The BSP defaults may need to be adjusted using configure
BSP
options to match the size of memory your board may have.
8.2.22.1. Bootloader¶
The bootloader initialises the Zynq device. The Xilinx tool provide an
interface to configure the hardware. This is includes the buses,
clocks, memory and UART board rate. The output of this is called
ps7_init
and it a C file. The Xilinx SDK builds a first stage boot
loader (FSBL) using this file.
The U-Boot boot loader has it’s own FSBL called MLO
to initialise
the hardware.
8.2.22.2. Clocks¶
An application can provide a function called:
uint32_t a9mpcore_clock_periphclk(void);
to return the peripheral clock. Normally this is half the CPU
clock. This function is declared weak
so you can override the
default behaviour by providing it in your application.
8.2.22.3. Console¶
The console driver for the UARTs will always be initialized to a baud rate of 115200 with 8 bit characters, 1 stop bit and no parity bits during start up. Previous configurations programmed into the hardware by the Xilinx tools or a bootloader will be overwritten.
The settings for the console driver can be changed by the user application through the termios API afterwards.
8.2.22.4. Network¶
The Cadence network interface driver of LibBSD works on the Xilinx Zynq
platform. The hardware checksum support works on real hardware but does not
seem to be supported on Qemu therefore the default state is to disable
IFCAP_TXCSUM
and IFCAP_RXCSUM
and this can be enabled from the shell
with:
ifconfig cgem0 rxcsum txcsum
or with an ioctl()
call to the network interface driver with SIOCSIFCAP
and the mask IFCAP_TXCSUM
and IFCAP_RXCSUM
set.
8.2.22.5. Debugging with xilinx_zynq_a9_qemu¶
To debug an application add the QEMU options -s
. If you need to
debug an initialisation issue also add -S
. For example to debug a
networking application you could use:
qemu-system-arm -M xilinx-zynq-a9 -m 256M -no-reboot -serial \
null -serial mon:stdio -nographic \
-net nic,model=cadence_gem -net vde,id=vde0,sock=/tmp/vde1 \
-kernel myapp.exe \
-s -S
Start GDB with the same executable QEMU is running and connect to the QEMU GDB server:
(gdb) target remote :1234
If your application is crashing set a breakpoint on the fatal error handler:
(gdb) b bsp_fatal_extension
Enter continue to run the application. Running QEMU loads the
executable and initialises the CPU. If the -S
option is provided
the CPU is held in reset. Without the option the CPU runs starting
RTEMS. Either way you are connecting to set up target and all you need
to do is continue:
(gdb) c
If you have a crash and the breakpoint on bsp_fatal_extension
is
hit, load the following a GDB script:
define arm-crash
set $code = $arg0
set $r0 = ((const rtems_exception_frame *) $code)->register_r0
set $r1 = ((const rtems_exception_frame *) $code)->register_r1
set $r2 = ((const rtems_exception_frame *) $code)->register_r2
set $r3 = ((const rtems_exception_frame *) $code)->register_r3
set $r4 = ((const rtems_exception_frame *) $code)->register_r4
set $r5 = ((const rtems_exception_frame *) $code)->register_r5
set $r6 = ((const rtems_exception_frame *) $code)->register_r6
set $r7 = ((const rtems_exception_frame *) $code)->register_r7
set $r8 = ((const rtems_exception_frame *) $code)->register_r8
set $r9 = ((const rtems_exception_frame *) $code)->register_r9
set $r10 = ((const rtems_exception_frame *) $code)->register_r10
set $r11 = ((const rtems_exception_frame *) $code)->register_r11
set $r12 = ((const rtems_exception_frame *) $code)->register_r12
set $sp = ((const rtems_exception_frame *) $code)->register_sp
set $lr = ((const rtems_exception_frame *) $code)->register_lr
set $pc = ((const rtems_exception_frame *) $code)->register_pc
set $cpsr = ((const rtems_exception_frame *) $code)->register_cpsr
end
Enter the command:
(gdb) arm-crash code
Enter bt
to see the stack back trace.
The script moves the context back to the crash location. You should be able to view variables and inspect the stack.
The fatal error handler runs inside an exception context that is not the one than generated the exception.